US 2008/0095421 A1 discloses the registration of two-dimensional (2D) X-ray fluoroscopic images with respect to coordinates of three-dimensional (3D) preoperative computed tomography (CT) or magnetic resonance (MR) images of a volume by registering the fluoroscopic images and the 3D images to 3D ultrasound coordinates. The fluoroscopic images are used for real-time monitoring of the medical procedure. The document further describes that the pre-operative CT and/or MR image data may be fused with the intra-operative 2D fluoroscopic images though 2D/3D registration techniques which are generally intensity-based, centerline-based, and landmark-based.
US 2016/0331338 A1 describes non-invasive methods and apparatus for combining 2D angiographic images with 3D scan data for radiosurgical target definition. A plurality of two-dimensional angiographic images with two or more orientations of an angiographic imaging system is acquired, wherein each of the plurality of 2D angiographic images includes a projection of a plurality of non-invasive fiducial markers having a known three-dimensional configuration. A processing device registers selected 2D angiographic images to a 3D scan volume produced by a 3D imaging system. In order to perform the registration, digitally reconstructed radiographs (DRRs) from the 3D scan volume can be generated using the imaging geometry of the two or more orientations of the angiographic imaging system. Selected DRRs are compared to selected 2D angiographic images and a transformation between the 3D scan volume and the 3D object space is found that maximizes a similarity measure between the selected DRRs and the selected angiographic images.
Using preoperative 3D images during surgery has the advantage that the surgeon can rely on images with a higher resolution, and therefore with more detailed image information, compared to X-ray images or other two-dimensional images, which are taken immediately before surgery or during surgery. Furthermore, the preoperative scan may produce image information about tissue that cannot be acquired by the 2D-imaging system.
A specific technical field is spine surgery, but the invention is also applicable with respect to other cases in which the object to be imaged comprises a plurality of rigid parts (for example bones) which are movably connected to each other, in most cases pairwise movable connected to each other. Preoperative image data on one hand and 2D image data taken immediately before or during treatment of the object on the other hand represent the plurality of rigid parts in different states of position and orientation relative to each other. For example two neighboring vertebras of the spine change their relative position and relative orientation when the patient moves. Therefore, the three-dimensional preoperative image data can only be used by the surgeon or technician for treatment (operation) if these limitations are observed.